FORENSIC BALLISTICS DR SALINI CHANDRAN BHMS HOD DEPT

FORENSIC BALLISTICS DR. SALINI CHANDRAN ; BHMS HOD; DEPT: OF FORENSIC MEDICINE & TOXICOLOGY

FORENSIC BALLISTICS • Science dealing with the investigation of firearms, ammunition and problems arising from their use

• In law, a firearm is defined as "a lethal barrelled weapon of any description from which any shot, bullet or missile can be discharged". • a better definition is that a firearm is an object with a barrel, through which a projectile or shot is discharged through the action of expanding gases from the burning of an explosive, or through the action of compressed air or gas which expands

CLASSIFICATION I. Rifled Weapons II. Smooth bored weapons

Rifled Weapons • 1. Rifles a)Air & gas operated rifles b)0. 22 rifles c)Military & sporting rifles • 2. Single shot target practice pistols • 3. Revolvers • 4. Automatic pistols • 5. True automatic weapons (machine guns)

II. SMOOTH BORED WEAPONS (shotgun) • Single barrel • Double barrel Over-bolt Action According to firing action Under-bolt Action • Lever –Action Pump Action or Autoloading Model

SIGHT PARTS OF A FIREARM REAR SIGHT

• Shotgun: A gun with a smoothbore barrel and is fired from the shoulder using both hands • shoots cartridges that contain "shot" or small metal pellets (of lead or steel) as the projectiles • Shotguns have a much shorter range than most rifles or pistols • Double barrel: Two barrels side by side or one on top of the other, usually on a shotgun.

SHOTGUN • M May be single –barrelled or double –barrelled • Shotguns have a similar external appearance to rifles, but differ in the lack of rifling inside the barrel, • A shotgun shell may contain one large projectile (called a slug), a few pellets of large shot, or many tiny pellets. • Barrel length-55 -72 cm • Common gauges-12, 16, 20

• "Rifle" - a rifle is a firearm with a stock and a rifled barrel which is fired using both hands and is shoulder-mounted

MUSKET Smooth bored, long barrelled old type military guns with bayonet at the muzzle end

• The weapon is made to break open on hinge across the breech facing for insertion and extraction of cartridge cases • Muzzle loading-loaded from muzzle • Lack rifling inside the barrel • Cylinder bore- diameter when same throughout • Choke bore-distal 7 -10 cm is narrow • different degrees-full choke , three quarter choke, half choke , quarter choke, etc

Degree of choking Degree of constriction Full choke 40/1000 th of an inch Three quarter choke 30/1000 th of an inch Half choke 20/1000 th of an inch Quarter choke 10/1000 th of an inch Improved cylinders 3 -5/1000 th of an inch

PARADOX GUNS • Smooth-Bored guns in which the inner surface of the barrel near the muzzle is grooved like rifles

• "Rifle" - a rifle is a firearm with a stock and a rifled barrel which is fired using both hands and is shoulder-mounted • Shotgun: A gun with a smoothbore that shoots cartridges that contain "shot" or small metal pellets (of lead or steel) as the projectiles • Revolver: Handgun that has a cylinder with holes to contain the cartridges. The cylinder revolves to bring the cartridge into position to be fired. • This is "single-action" when the hammer must be cocked before the trigger can fire the weapon. • It is "double-action" when pulling the trigger both cocks and fires the gun.

Revolver

Revolver

Machineguns" • "Machineguns" - this covers firearms such as assault rifles, submachine guns etc. • A machinegun is a firearm capable of firing successive shots with a single pull on the trigger

Assault rifle

"Handgun" • which includes a pistol, revolver, air pistol, muzzle-loading pistol, etc. • This is a firearm without a shoulder stock which is held and fired from a person's hand or hands, and is typically smaller than other types of firearm. • Also, most handguns have rifled barrels • Pistol: Synonym for a handgun that does not have a revolving cylinder.

Butt or buttstock: The portion of the gun which is held or shouldered Barrel: The metal tube through which the bullet is • Barrel: The metal tube through which the fired. bullet is fired. Chamber: The portion of the "action" that holds the cartridge ready for firing. Bore: The inside of the barrel. "Smoothbore" weapons (typically shotguns) have no rifling. Most handguns and rifles have "rifling". Breech: The end of the barrel attached to the action. Magazine: This is a device for storing cartridges in a repeating firearm for loading into the chamber. Also referred to as a "clip"

• Stock: A wood, metal, or plastic frame that holds the barrel and action and allows the gun to be held firmly. • Hammer: A metal rod or plate that strikes the cartridge primer to detonate the powder. • Muzzle: The end of the barrel out of which the bullet comes. • Choke: A constriction of a shotgun bore at the muzzle that determines the pattern of the fired shot

• Safety: A mechanism on an action to prevent firing of the gun. • Cartridge: Also called a "round". Made up of a case, primer, powder, and bullet.

Cartridge Rimmed, centerfire. 303 in cartridge from WWII. • Cartridge or round packages the bullet • , gunpowder and primer into a single metallic case • precisely made to fit the firing chamber of a firearm • The primer is a small charge of impact-sensitive chemical that may be located at the center of the case head (centerfire ammunition) or at its rim (rimfire ammunition).

Cartridge • 1. the bullet itself 2. the casing, which holds all parts together 3. the explosive, for example gunpowder 4. the rim, at the base of the cartridge 5. the primer, which ignites the gunpowder

• Gauge: Refers to the diameter of the barrel on a shotgun in terms of the number of lead balls the size of the bore it would take to weigh one pound (454 gm) (10 gauge, 12 gauge, etc. ) • Caliber: The diameter of the bore measured from land to land, usually expressed in hundredths of an inch (. 22 cal) or in millimeters (9 mm).

• Lead: Simple cast, extruded, swaged, or otherwise fabricated lead slugs are the simplest form of bullets • Jacketed Lead: Bullets intended for highvelocity applications generally have a lead core jacketed or plated with copper or steel; the thin layer of copper protects the lead core during flight, delivering it intact to the target. • Armor Piercing: Jacketed designs where the core material is a very hard and highdensity metal such as tungsten, tungsten carbide, depleted uranium, or steel. M A T E R I A L

• Ignition: The way in which powder is ignited. Old muzzle-loading weapons used flintlock or percussion caps. Modern guns use "primers" that are "rimfire" or "centerfire“ • Centerfire: The cartridge contains the primer in the center of the base, where it can be struck by the firing pin of the action. • "Rimfire" cartridges have primer inside the base, • while "centerfire" cartridges have primer in a hole in the middle of the base of the cartridge case.

• Magnum: An improved version of a standard cartridge which uses the same caliber and bullet, but has more powder, giving the fired bullet more energy. Magnum shotgun loads, however, refer to an increased amount of shot pellets in the shell. • Silencer: A device that fits over the muzzle of the barrel to muffle the sound of a gunshot. • Most work by baffling the escape of gases.

Powder: Modern gun cartridges use "smokeless" powder that is relatively stable, of uniform quality, and leaves little residue when ignited. Black Powder: The old form of gunpowder invented over a thousand years ago and consisting of nitrate, charcoal, and sulfur. For centuries, "black powder" was used and was quite volatile (ignited at low temperature or shock), was composed of irregularly sized grains, and left a heavy residue after ignition, requiring frequent cleaning of bore

• Primer: A volatile substance that ignites when struck to detonate the powder in a cartridge. • Smokeless powder: Refers to modern gunpowder, which is really not "powder" but flakes of nitrocellulose and other substances. Not really "smokeless" but much less so than black powder.

Bullets:

Tracer: These have a hollow back, filled with a flare material Usually this is a mixture of magnesium, perchlorate, and chromium, to yield a bright red color Incendiary: These bullets are made with an explosive or flammable mixture in the tip which is designed to ignite on contact with a target. The intent is to ignite fuel in the target area and add to the destructive power of the bullet itself.

• Frangible: Designed to disintegrate into tiny particles upon impact to minimize their penetration for reasons of range safety, to limit environmental impact, or to limit the danger behind the intended target

• "round-nose" - The end of the bullet is blunted. • "hollow-point" - There is a hole in the bullet that creates expansion when a target is struck, creating more damage. • "jacketed" - The soft lead is surrounded by another metal, usually copper, that allows the bullet to penetrate a target more easily. • "wadcutter" - The front of the bullet is flattened. • "semi-wadcutter" - Intermediate between roundnose and wadcutter. • "semi-wadcutter" - Features of both semiwadcutter and hollowpoint.

"Handgun" • which includes a pistol, revolver, air pistol, muzzle-loading pistol, etc • This is a firearm without a shoulder stock which is held and fired from a person's hand or hands, and is typically smaller than other types of firearm. • Also, most handguns have rifled barrels

BALLISTICS • The term ballistics refers to the science of the travel of a projectile in flight. • The flight path of a bullet includes: travel down the barrel, path through the air, and path through a target.

• The cartridge seals a firing chamber in all directions except down the bore. • A firing pin strikes the primer, igniting it. The spark from the primer ignites the powder. • Burning gases from the powder expand the case to seal against the chamber wall. • The projectile is then pushed in the direction that releases this pressure, down the barrel. • After the projectile leaves the barrel the pressure is released and the cartridge case is pulled out of the chamber.